♻️ Polish Implementation of SC QDMI Device

[ystade]

As pointed out by @burgholzer in #1328 (comment)_, the implementation of the initial, minimalistic SC device needs to be further polished. In particular, this involves:

• Proper handling of operations
• Fideltity data for the sites

[coderabbitai]

As noted in PR #1328, the testPopulation helper function is duplicated between test/na/device/test_generator.cpp and test/qdmi/sc/test_generator.cpp. As part of this refactoring issue, consider extracting this helper to a shared test utility (e.g., test/qdmi/test_utils.hpp) to reduce duplication across device backends.

Related: #1328 (comment)